Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[etudiant]

Seems clear enough from Tsutsuji-san's postings:

http://mainichi.jp/select/jiken/news...40092000c.html Beta radiations due to strontium and other substances are between 100,000 Bq/cm³ and 1,000,000 Bq/cm³. The strontium concentration in the leaked water is about one million times as high as the standard set by the nuclear power regulating law for sea releases.The building's area is 30 m x 30 m. As the leaked water's height was about 5 cm, the leak's volume is 30 x 30 x 0.05 = 45 m³.

In all, as much as 220 tons of water may now have leaked from the facility, according to a report in the Asahi Shimbun newspaper that cited Tepco officials.
http://www.nytimes.com/2011/12/05/wo...ear-plant.html

The thing that throws a US reader is the reference to a 'puddle' of contaminated water, which does not convey the same impression as learning of a 45 ton or even 200 ton leakage.
In fairness to TEPCO, they have thus far treated some 180,000 tons of water, so perhaps by that standard, the term 'puddle' is quite appropriate.

 

[Joffan]

etudiant; absolutely clear on the volume now. I don't know how I missed it.

 

[Caniche]

5.8 trillion becquerels ! As far as leaks go ,how would this score on the INES scale ?

Is there much point in TEPCO just reducing cesium contamination and leaving other isotopes undiminished? Did that official really drink all that strontium?

 

[rmattila]

As far as I understand, the leak is in the last stage of the process, where the salty waste liquid produced in the reverse osmosis is further concentrated by evaporation. And apparently it is from the more concentrated side of that process as well. Certainly not from the water that's being recycled into the reactors.

As to why they are leaving it as liquid, I'm no chemist but assume that it might have something to do with the high salt content messing up the possibilities to extract strontium from the liquid, and it is therefore for time being stored as it is.

The amount of leak appears to be somewhat unclear: I got the impression that the 45 tons would be the amount found inside the building - I don't now how that relates to the amount that has actually leaked outside or found its way to the sea.

 

[tsutsuji]

http://www3.nhk.or.jp/news/html/20111205/t10014421611000.html Concerning strontium, the analysis takes about two weeks. The NISA requests Tepco to write a report on the cause of the leak and on countermeasures. The water leaked for 21 hours or less before Tepco found it. A concrete barrier recently installed to contain leaks, had cracks.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111205_01-e.pdf Status of the water leakage

http://mainichi.jp/select/biz/news/20111206k0000m040083000c.html According to Tepco, 300 l flowed outside the building.

 

[joewein]

Did that official really drink all that strontium?

You are probably thinking about Yasuhiro Sonoda, parliamentary secretary at the cabinet office who drank water in front of journalists about 5 weeks ago.

That water was not from the basements of the wrecked units 1-3, where the water in this current leak originates from. It was from units 5 and 6, whose fuel rods are still intact, as one air-cooled diesel in unit 6 survived the tsunami to provide power for the cooling.

 

[SteveElbows]

I just noticed that the recent core melt analysis stuff is available in english:http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_04-e.pdf
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_05-e.pdf
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_06-e.pdf
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_07-e.pdf
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_08-e.pdf

Not had time to read it all yet but as per my earlier post based on the Japanese version, we see a repeat of stuff first mentioned a long time ago but not dwelled upon that much, such as a presumption that there was a drywell leak 22 hours after the earthquake at reactor 2. And somewhere they also mention one of the subjects that interests me, why the reactor 2 suppression chamber water temperature readings went up in the latter part of October - they say its because after water injection rate was increased, steam decreased so there was more hot water ending up in the suppression chamber. Speaking of which, I see that s/c temperatures at 2 have started creeping up again in recent days after falling for quite some time.

 

[elektrownik]

I don't understand one thing, from those analysis we can see that tepco think that part of unit 2 core is still undamaged, but I see problem here, they also recalibrated water level sensor and from data we can see that it is -5m from top of 4m fuel rods. So it is possible that fuel will not melt without cooling ?

 

[Shinjukusam]

I don't understand one thing, from those analysis we can see that tepco think that part of unit 2 core is still undamaged, but I see problem here, they also recalibrated water level sensor and from data we can see that it is -5m from top of 4m fuel rods. So it is possible that fuel will not melt without cooling ?

Good point, it's possible that if that level is accurate and there is still standing material then the rising steam is sufficient to provide a modicum of cooling.
That is dependent on their hypothesis being correct, of course.

 

[tsutsuji]

I just noticed that the recent core melt analysis stuff is available in english:http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_04-e.pdf
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_05-e.pdf
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_06-e.pdf
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_07-e.pdf
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_08-e.pdf

These are the press conference / workshop slides. The the main report ( http://www.tepco.co.jp/nu/fukushima-np/images/handouts_111130_09-j.pdf ) (207 pages) is still not available in English.

"All fuel melted through PCV from　original position" on page 20 of http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_04-e.pdf is presumably a translation mistake. The Japanese text at http://www.tepco.co.jp/nu/fukushima-np/images/handouts_111130_07-j.pdf says "all fuel moved downwards from original position". Then, "Further, as there is a high probability that RPV damage occurred, we estimate that a considerable amount dripped down to PCV bottom".

 

[zapperzero]

I don't understand one thing, from those analysis we can see that tepco think that part of unit 2 core is still undamaged, but I see problem here, they also recalibrated water level sensor and from data we can see that it is -5m from top of 4m fuel rods. So it is possible that fuel will not melt without cooling ?

I don't see where they say that?

Given current water levels and the fact that they estimate that less than 3% of fuel is uncovered, it would seem that all the fuel has relocated to the bottoms of the RPVs in units 2&3 and even further to the bottom of the PCV in the case of Unit 1.

 

[Rive]

I don't see where they say that?

Given current water levels and the fact that they estimate that less than 3% of fuel is uncovered, it would seem that all the fuel has relocated to the bottoms of the RPVs in units 2&3 and even further to the bottom of the PCV in the case of Unit 1.

Well, in http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_04-e.pdf they state that

Even though the fuel was damaged and melted , a part of the fuel remains inside the core of RPV and the others dropped to the bottom of RPV plenum or the PCV pedestal.

.

I think the 'uncovered' is just a translation error and they mean 'uncooled'.

 

[tsutsuji]

I don't see where they say that?

See the green colour squares labelled "Damaged fuel piled (Maintain of fuel rod figure)" on page 8 (9/29) of http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_08-e.pdf

Given current water levels and the fact that they estimate that less than 3% of fuel is uncovered, it would seem that all the fuel has relocated to the bottoms of the RPVs in units 2&3 and even further to the bottom of the PCV in the case of Unit 1.

I agree. The "3% (or less) uncovered" result and the "Unit 2 result of estimation with analysis code" ( page 8 (9/29) of http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_08-e.pdf ) seem to contradict each other.

"Therefore, it is evaluated that all the moved fuel is expected to be cooled directly by water injection." written on page 23 (24/28) of http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_04-e.pdf could alternatively be translated as "Therefore, it is evaluated that all the moved fuel is being cooled in a condition where it is largely in contact with water". It sounds like that the question of how the unmoved fuel is being cooled is left unanswered.

I think the 'uncovered' is just a translation error and they mean 'uncooled'.

Well, after reading http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_06-e.pdf it seems that they mean just the opposite, because they say :

Considering the results that water injection from the core spray system exerted a great effect (...) In the new model, a part of the injected water directly removes the heat from the uncovered core.
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_06-e.pdf page 2 (3/10)

It sounds like that what they mean by "uncovered" means "uncovered and cooled by core spray system or cooled by heat conduction/convection/radiation".

 

[zapperzero]

See the green colour squares labelled "Damaged fuel piled (Maintain of fuel rod figure)" on page 8 (9/29) of http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_08-e.pdf

Yeah, they're saying it should look a bit like TMI on the inside, which does not seem to be consistent with their other estimates.

 

[tsutsuji]

Yeah, they're saying it should look a bit like TMI on the inside, which does not seem to be consistent with their other estimates.

Even their "Conservative scenario Approx.109 hours after the earthquake" on page 8 (9/29) of http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_08-e.pdf has 12 little orange squares above original bottom of fuel. That makes 12% and this is still higher than the 3% result from the "improved JAEA heat model" explained on http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_06-e.pdf

The other scenario translated as "Based on the indicator" on the English version can alternatively be translated as "relying on indicated values".

 

[Rive]

It sounds like that what they mean by "uncovered" means "uncovered and cooled by core spray system or cooled by heat conduction/convection/radiation".

Yeah, thanks. You are right.

3%... I thought it'll be more than that: the change when they switched on the CSS was really impressive.

Of course the cooling of the covered fuel was also improved by the water amount pushed in through the CSS, so it's logical... But a bit sad.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20111206/index.html According to Tepco, about 150 litres of water contaminated with beta-radiating substances such as strontium flowed to the sea. A maximum of 300 litres flowed through the cracks in the building's foundation. The 150 litre figure is the result of an estimate based on data such as leaking time.

The density of radioactive materials contained in the water leaked is 2.6 x 10^10 Becquerel (provisional) in total, calculating from
the density of strontium 89, 90, cesium 134, and 137.

Strontium 89: 7.4 x 10^4 Bq/cm3 (1.1 x 10^10 Bq)
Strontium 90: 1.0 x 10^5 Bq/cm3 (1.5 x 10^10 Bq)
Cesium 134: 1.6 x 10^1 Bq/cm3 (2.4 x 10^6 Bq)
Cesium 137: 2.9 x 10^1 Bq/cm3 (4.4 x 10^6 Bq)
(Water collected on Dec 4, 2011. Amount of strontium estimated from the density of all-beta radioactive materials.)

This value accounts for 12 % of 2.22 x 10^11 Bq, which is the annual discharge control target of radioactive liquid waste at
Fukushima Daiichi Nuclear Power Station.
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/111206e16.pdf

http://www3.nhk.or.jp/news/genpatsu-fukushima/20111206/1910_reikyaku.html Suspecting that it caused a delay in the response to the accident, the NISA investigated and heard witnesses in August on the question whether plant managers had mistakenly believed unit 1's isolation condenser was running while it was not. The results of the NISA's investigation were publicly released on 6 December : the managers were not aware that a plant operator had closed the IC's valve, and it is 8 hours after the earthquake, after 11 PM, after knowing that the radiation inside reactor building was rising, that they first grasped the IC status. It is possible that this caused a delay in the response to the accident.

The documents released by the NISA:

http://www.meti.go.jp/press/2011/12/20111206002/20111206002-2.pdf List of questions (asked by the NISA to the witnesses)

http://www.meti.go.jp/press/2011/12/20111206002/20111206002-3.pdf The NISA's conclusions

(they cover a wide range of topics, not only unit 1, not only unit 1's IC)

 

[Pakman]

I just noticed that the recent core melt analysis stuff is available in english:

It seems they don't take into account the additional heat from the steam-zirconium exothermic reaction.There suppose to be hydrogen at unit 3 at least, so some part of zirconium reacted. How much?

 

[Caniche]

You are probably thinking about Yasuhiro Sonoda, parliamentary secretary at the cabinet office who drank water in front of journalists about 5 weeks ago.

That water was not from the basements of the wrecked units 1-3, where the water in this current leak originates from. It was from units 5 and 6, whose fuel rods are still intact, as one air-cooled diesel in unit 6 survived the tsunami to provide power for the cooling.

Cheers Joe , I'm convinced you are spot on dead accurate.
Question is ,what impression "TEPCO" are trying to convey to the general public.;)

 

[SteveElbows]

And somewhere they also mention one of the subjects that interests me, why the reactor 2 suppression chamber water temperature readings went up in the latter part of October - they say its because after water injection rate was increased, steam decreased so there was more hot water ending up in the suppression chamber. Speaking of which, I see that s/c temperatures at 2 have started creeping up again in recent days after falling for quite some time.

Oops I made a mistake. The documents were talking about the temperature rise of reactor 1 suppression chamber in the past, not reactor 2. I think they mentioned reactor 3 s/c temp as well.

The interesting temperatures mentioned for reactor 2 are the ones for the CRD housing, and SRV, some of which are much higher than the other temperatures we are used to seeing regular data about. (page 6 of http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_05-e.pdf )

 

[rowmag]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20111206/index.html According to Tepco, about 150 litres of water contaminated with beta-radiating substances such as strontium flowed to the sea. A maximum of 300 litres flowed through the cracks in the building's foundation. The 150 litre figure is the result of an estimate based on data such as leaking time.

The density of radioactive materials contained in the water leaked is 2.6 x 10^10 Becquerel (provisional) in total, calculating from
the density of strontium 89, 90, cesium 134, and 137.

Strontium 89: 7.4 x 10^4 Bq/cm3 (1.1 x 10^10 Bq)
Strontium 90: 1.0 x 10^5 Bq/cm3 (1.5 x 10^10 Bq)
Cesium 134: 1.6 x 10^1 Bq/cm3 (2.4 x 10^6 Bq)
Cesium 137: 2.9 x 10^1 Bq/cm3 (4.4 x 10^6 Bq)
(Water collected on Dec 4, 2011. Amount of strontium estimated from the density of all-beta radioactive materials.)

Why is there so much strontium relative to cesium there, when there is so little strontium relative to cesium seen outside the plant? Strontium doesn't become airborne as easily, I presume?

 

[etudiant]

The leakage afaik is from the residual water left over after treatment by the Kurion and Toshiba ion exchange lines, as well as the AREVA line, if that is still in use. That water is then desalinated and the brine left over, which contains the unrecovered nucleotides such as strontium, is stored pending an evaporation process to reduce the residual volume.
It is interesting to see the relatively minimal cesium content of this residue. It seems the water clean up process is pretty effective, with cesium down to about one millionth of the starting contamination.

 

[rowmag]

Ah, of course, silly me.

 

[gmax137]

... nucleotides ...

Please, it is 'nuclides', not http://en.wikipedia.org/wiki/Nucleotide

 

[etudiant]

Please, it is 'nuclides', not http://en.wikipedia.org/wiki/Nucleotide

My bad.
Nuclides it is, we are not leaking little bits of DNA from TEPCO's genetic engineering facility.

 

[Rive]

Can somebody please link a press release/report/something about PCV gas contents? Not about the nuclides but about all the components.

I've just noticed that 'no CO2' and 'no sign of CCI' are stated sometimes, but I could not find any detailed report about regular measurements.

 

[tsutsuji]

Can somebody please link a press release/report/something about PCV gas contents? Not about the nuclides but about all the components.

I've just noticed that 'no CO2' and 'no sign of CCI' are stated sometimes, but I could not find any detailed report about regular measurements.

On http://www.tepco.co.jp/nu/fukushima-np/images/handouts_111130_09-j.pdf page 13 (17/207), table 4.4-1 provides some hydrogen, carbon monoxide and carbon dioxide concentrations in unit 1 and unit 2 PCVs. (key: 1号: unit 1　2号: unit 2　8月: August　9月:September). This table is commented on page 8 (12/207) where they say that these amounts of carbon dioxide are nothing more than the part which is naturally carried by water, and they conclude that the core-concrete reaction had been stopped at the time of those measurements. They provide more detailed explanations in attachment 14 (pages 194/207 to 199/207) and attachment 15 (page 200/207 to 206/207). Attachment 14 is named "Results of analysis of gasses compositions inside PCVs". It concerns the following samples :

No.1,2,3 : three gas samples taken on 29 July at unit 1
No.4,5,6 : three gas samples taken on 9 August at unit 2
No.7,8,9 : three gas samples taken on 14 September at unit 1
No.10 : an air sample from outside

There is also an estimate of the CO2 levels that should be expected in case of core-concrete reaction.

Attachment 15 is named "Residual gasses remaining from early accident"

 

[zapperzero]

they say that these amounts of carbon dioxide are nothing more than the part which is naturally carried by water, and they conclude that the core-concrete reaction had been stopped at the time of those measurements.

One of the assumptions here is that significant amounts of gas from a corium-concrete reaction would necessarily end up in the cooling water. Is this true, I wonder?

 

[Rive]

...

Thanks.

I wonder how often they are checking the levels.

 

[tsutsuji]

The strontium leak:

http://www.tepco.co.jp/en/press/corp-com/release/11120806-e.html Report on response to the accident due to the leakage of water containing radioactive materials at the water desalination (evaporative concentration apparatus) of Fukushima Daiichi Nuclear Power Station to NISA. (24 pages, English) ("it will take nearly one month to obtain result of the analysis of Strontium in the leaked water")

"Concept of Securing the Mid-Term Safety":

http://www3.nhk.or.jp/news/genpatsu-fukushima/20111209/1700_hoanin.html The NISA has approved Tepco's mid term safety plan for the next 3 years. The NISA heard the opinions of specialists at a meeting on 9 December. Some specialists expressed the view that more should be done to find out the fuel condition "such as using infrared measurements", but the NISA said that as an urgent response, the plan was valid. Kazuhiko Kudo of Kyushu university said "only minimal safety countermeasures are implemented, and more efforts should be done to secure safety ". The NISA must then report the plan to the NSC, and upon NSC approval, all the conditions for completion of "step 2" are met. http://www.tepco.co.jp/en/press/corp-com/release/11120814-e.html Report with regards to "Policy on the mid term security" for the Units 1 to 4 of Fukushima Daiichi Nuclear Power Station to Nuclear and Industrial Safety Agency at the Ministry of Economy, Trade and Industry (part 2) (8 December 2011, English press release linking to a 159 page Japanese report)

http://www.tepco.co.jp/en/press/corp-com/release/11120701-e.html Report with regards to "Policy on the mid term security" for the Units 1 to 4 of Fukushima Daiichi Nuclear Power Station to Nuclear and Industrial Safety Agency at the Ministry of Economy, Trade and Industry (part 1) (revision 2) (7 December, English press release linking to Japanese report)

http://www.tepco.co.jp/en/press/corp-com/release/11110912-e.html Report with regard to "Policy on the mid term security" for the Units 1 to 4 of Fukushima Daiichi Nuclear Power Station to Nuclear and Industrial Safety Agency at the Ministry of Economy, Trade and Industry (part 1) (revision 1) (9 November, English press release linking to Japanese report)

http://www.tepco.co.jp/cc/press/11101702-j.html Report with regard to "Policy on the mid term security" for the Units 1 to 4 of Fukushima Daiichi Nuclear Power Station to Nuclear and Industrial Safety Agency at the Ministry of Economy, Trade and Industry (part 1) (17 October, Japanese)

http://www.nisa.meti.go.jp/english/press/2011/10/en20111020-2.pdf Regarding the Receipt of Report from TEPCO and Holding Hearings on “The Concept of Securing the Mid-Term Safety” for Units 1 to 4 at Fukushima Dai-ichi Nuclear Power Station, Tokyo Electric Power Co., Inc.(October 17, 2011, English)

http://www.nisa.meti.go.jp/english/press/2011/10/en20111019-2.html Regarding the Direction on “The Concept of Securing the Mid-Term Safety” for Units 1 to 4 at Fukushima Dai-ichi Nuclear Power Station, Tokyo Electric Power Co., Inc. (October 3, 2011, English)

 

[joewein]

One of the assumptions here is that significant amounts of gas from a corium-concrete reaction would necessarily end up in the cooling water. Is this true, I wonder?

I also wonder how much extra CO2 would be released from concrete melted by corium once it's gone much beyond penetrating the concrete surface.

It was under the impression that CO2 from air reacts with concrete mostly at the surface exposed to air and that deeper inside there would be far less CaCO3. Partly this is because it was mentioned in one of the threads here before that broken concrete (as in shattered bits that fell into spent fuel pools at unit 3 or 4) is highly alkaline because deep inside it still contains a lot of alkaline CaO.

When CaCO3 gets heated to be white hot (~1000C) it releases CO2, but how much CaCO3 is there 65 cm below the surface? Is it at all valid to deduct from CO2 levels that the reaction stopped at that depth?

 

[zapperzero]

When CaCO3 gets heated to be white hot (~1000C) it releases CO2, but how much CaCO3 is there 65 cm below the surface? Is it at all valid to deduct from CO2 levels that the reaction stopped at that depth?

http://koti.welho.com/tsevon/mcci.pdf

Siliceous concrete releases mainly water vapor, while calcareous concrete releases also substantial amounts of carbon dioxide.

 

[joewein]

I see what I missed. Concrete is made from a mix of cement, aggregate, sand and water. I was only thinking about the chemistry of cement and water (plus air), but the aggregate may contain carbonate rocks (such as limestone or dolomite) too.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20111212/index.html While commenting that "the reactors are still in the the way towards stable condition, and the possibility of troubles is remaining", and that "[the effort] shall expand over a long duration, and the durability of the equipment must be inspected", the NSC (Nuclear Safety Commission of Japan) approved Tepco's mid term safety plan. The "cold shutdown" status is expected to be announced by the Japanese government on 16 December.

http://www.nsc.go.jp/info/20111212_dis.pdf The main lines of the NSC's examination of Tepco's mid-term safety plan (Japanese)

 

[falcon32]

Has anyone seriously considered creating small reservoirs next to our many piles of stored spent rods in the event that the power in the United States fails, and we need to cool them by a gravity-fed system until generators to power pumps are working?